(just thinking about how when I stomp around in the northern forest, which I do daily, I avoid the swampy bits and stick to the dry bits to avoid getting really stuck in the mud. I can't imagine getting through the swamp with a canoe.)
My experience of virgin forest is that it's totally impassible - fallen trees and dense understory everywhere - really really difficult to move through, but perhaps I've just got a biased view due to low samples.
On the other hand I definitely don't think that humans would have had an easy time going through a swamp - but instead round the edges with access into the land up rivers for trapping and camping.
It's true that to move and navigate effectively you have to be super familiar with that style of environment. You have to be planning your route from what you can see no more than a dozens or perhaps a hundred metres ahead. And thick clothes really helps. It clicks when you realise you can just push through a lot of stuff. Its the kind of thing that soldiers get sent on exercise to learn by immersion.
Of course the early humans would have been probably as in-tune as the best trackers and bushcraft survival experts today, and hide makes really good clothing.
